Just because a Power Card's Power number is red and spiky (maybe they all are; I haven't looked) doesn't mean it can only be used to substitute for a strength-battle roll yeah? We can use that number instead of rolling the dice for any check (skill, movement, etc).

"Immediately before a player is

required to roll a die to make a movement, battle, or
skill roll, he may declare that he is playing a Power card
instead." (p. 16)

So for example if you have to roll for a board space (Chaos Titan Mals Furia on the Inner Tier for example, three spaces on the Outer Tier that I can recall), can't use a Power card.